In the 1970s, the U.S. Air Force began looking for a replacement for its Lockheed C-130 Hercules tactical cargo aircraft.[3] The Advanced Medium STOL Transport (AMST) competition was held, with Boeing proposing the YC-14, and McDonnell Douglas proposing the YC-15.[4] Though both entrants exceeded specified requirements, the AMST competition was canceled before a winner was selected. The Air Force started the C-X program in November 1979 to develop a larger AMST with longer range to augment its strategic airlift.[5]

By 1980, the USAF found itself with a large fleet of aging C-141 Starlifter cargo aircraft. Compounding matters, USAF needed increased strategic airlift capabilities to fulfill its rapid-deployment airlift requirements. The USAF set mission requirements and released a request for proposals (RFP) for C-X in October 1980. McDonnell Douglas elected to develop a new aircraft based on the YC-15; Boeing bid an enlarged three-engine version of its AMST YC-14. Lockheed submitted two designs, a C-5-based design and an enlarged C-141 design. On 28 August 1981, McDonnell Douglas was chosen to build its proposed aircraft, then designated C-17. Compared to the YC-15, the new aircraft differed in having swept wings, increased size, and more powerful engines.[6] This would allow it to perform the work done by the C-141, and also fulfill some of the duties of the Lockheed C-5 Galaxy, freeing the C-5 fleet for outsize cargo.[6]

Alternate proposals were pursued to fill airlift needs after the C-X contest. These were lengthening of C-141As into C-141Bs, ordering more C-5s, continued purchases of KC-10s, and expansion of the Civil Reserve Air Fleet. Limited budgets reduced program funding, requiring a delay of four years. During this time contracts were awarded for preliminary design work and for the completion of engine certification.[7] In December 1985, a full-scale development contract was awarded.[8] At this time, first flight was planned for 1990.[7] The Air Force had formed a requirement for 210 aircraft.[9]

Development problems and limited funding caused delays in the late 1980s.[10] Criticisms were made of the developing aircraft and questions were raised about more cost-effective alternatives during this time.[11][12] In April 1990, Secretary of Defense Dick Cheney reduced the order from 210 to 120 aircraft.[13] The maiden flight of the C-17 took place on 15 September 1991 from the McDonnell Douglas's plant in Long Beach, California, about a year behind schedule.[14][15] The first aircraft (T-1) and five more production models (P1-P5) participated in extensive flight testing and evaluation at Edwards Air Force Base.[16] Two complete airframes were built for static and repeated load testing.[15]

A static test of the C-17 wing in October 1992 resulted in the wing failing at 128% of design limit load, which was below the 150% requirement. Both wings buckled rear to the front and failures occurred in stringers, spars and ribs.[17] Some $100 million was spent to redesign the wing structure; the wing failed at 145% during a second test in September 1993.[18] A careful review of the test data however, showed that the wing was not loaded correctly and did indeed meet the requirement.[19] The C-17 received the "Globemaster III" name in early 1993.[6] In late 1993, the Department of Defense gave the contractor two years to solve production and cost overrun problems or face termination of the contract after the delivery of the 40th aircraft.[20] By accepting the 1993 terms, McDonnell Douglas incurred a loss of nearly US$1.5 billion on the development phase of the program.[16]

In April 1994, the C-17 program remained over budget, and did not meet weight, fuel burn, payload and range specifications. It failed several key criteria during airworthiness evaluation tests.[21][22][23] Technical problems were found with the mission software, landing gear, and other areas.[24] In May 1994, it was proposed to cut production to as few as 32 aircraft; these cuts were later rescinded.[25] A July 1994 GAO document revealed that Air Force and DoD studies from 1986 and 1991 stated the C-17 could use 6,400 more runways outside the U.S. than the C-5; it was discovered that these studies only considered runway dimensions, but not runway strength or Load Classification Numbers (LCN). The C-5 has a lower LCN, but the USAF classifies both in the same broad Load Classification Group (LCG). When considering runway dimensions and load ratings, the C-17's worldwide runway advantage over the C-5 shrank from 6,400 to 911 airfields.[26] The C-17's ability to use low quality, austere airfields was not considered.[26]

A January 1995 GAO report revealed that, over the original cost of $41.8 billion for 210 C17s, the 120 aircraft on order were costing $39.5 billion.[27] In March 1994, the U.S. Army decided it did not need the 60,000 lb (27,000 kg) Low Altitude Parachute Extraction System (LAPES) delivery with the C-17 and that the C-130's 42,000 lb (19,000 kg) capability was sufficient; C-17 testing was limited to this lower weight. Airflow issues prevented the C-17 from meeting airdrop requirements. A February 1997 GAO report revealed that a C-17 with a full payload could not land on 3,000 ft (910 m) wet runways; simulations suggested 5,000 ft (1,500 m) was required.[28] The YC-15 was transferred to AMARC to be made flightworthy again for further flight tests for the C-17 program in March 1997.[29] In 1995, most of the problems had been reportedly resolved.[30][31] The first C-17 squadron was declared operational by the USAF in January 1995.[32]

C-17s from the 517th Airlift Squadron dropping equipment and airborne infantry during joint training in September 2010.

In 1996, DoD ordered another 80 aircraft for a total of 120.[33] In 1997 McDonnell Douglas merged with its former competitor, Boeing. In April 1999, Boeing proposed to cut the price of the C-17 if the Air Force bought 60 more,[34] and in August 2002, the order was increased to 180 aircraft.[35] In 2007, 190 C-17s were on order for the USAF.[36] On 6 February 2009, Boeing was awarded a $2.95 billion contract for 15 additional aircraft, increasing the total USAF C-17 fleet to 205 and extending production from August 2009 to August 2010.[37] On 6 April 2009, U.S. Secretary of Defense Robert Gates stated that there would be no more C-17s ordered beyond the 205 planned.[38] However, on 12 June 2009, the House Armed Services Air and Land Forces Subcommittee added a further 17 C-17s.[39]

In 2010, Boeing transitioned to a production rate of 10 C-17s per year from a high of 16 per year, this was due to dwindling orders and to extend the life of the production line while additional international orders were sought. The workforce was reduced by approximately 1,100 through 2012, and a second shift at the Long Beach assembly plant was also eliminated.[40] By April 2011, 230 production C-17s had been delivered, including 210 to the USAF.[41] The C-17 prototype "T-1" was retired in 2012 after being used by the USAF for testing and development.[42] In January 2010, the USAF announced the end of Boeing's performance-based logistics contracts to maintain the aircraft.[43] On 19 June 2012, the USAF ordered its 224th and final C-17, as a replacement for an aircraft that crashed in Alaska in July 2010.[44]

In September 2013, Boeing announced that C-17 production was starting to close down. In October 2014, the main wing spar of the 279th and last aircraft was completed, this C-17 shall be delivered in 2015, after which Boeing will close the Long Beach plant.[45][46] Production of spare components shall continue until at least 2017. The C-17 is projected to be in service for several decades.[47][48] In February 2014, Boeing was engaged in sales talks with "five or six" countries for the remaining 15 C-17s, "two to four" of which are not current operators,[49] and Boeing decided to build 10 aircraft without confirmed buyers in anticipation of future purchases. As of April 2015[update], five aircraft found buyers, including two for the Middle East, two for Australia and one for Canada.[50]

In May 2015, the Wall Street Journal reported that Boeing expected to book a charge of under $100 million and cut 3,000 positions associated with the C-17 program. Teal Group analyst Richard Aboulafia suggested that Airbus' lower cost A400M Atlas has taken international sales away from the C-17.[51]

The C-17 is 174 feet (53 m) long and has a wingspan of about 170 feet (52 m). It can airlift cargo fairly close to a battle area. The size and weight of U.S. mechanized firepower and equipment have grown in recent decades from increased air mobility requirements, particularly for large or heavy non-palletized outsize cargo.

The C-17 is powered by four Pratt & Whitney F117-PW-100turbofan engines, which are based on the commercial Pratt and Whitney PW2040 used on the Boeing 757. Each engine is rated at 40,400 lbf (180 kN) of thrust. The engine's thrust reversers direct engine exhaust air upwards and forward, reducing the chances of foreign object damage by ingestion of runway debris, and providing enough reverse thrust to back the aircraft up on the ground while taxiing. The thrust reversers can also be used in flight at idle-reverse for added drag in maximum-rate descents. In vortex surfing tests performed by C-17s, up to 10% fuel savings were reported.[54]

For cargo operations the C-17 requires a crew of three: pilot, copilot, and loadmaster. The cargo compartment is 88 feet (26.82 m) long by 18 feet (5.49 m) wide by 12 feet 4 inches (3.76 m) high. The cargo floor has rollers for palletized cargo but it can be flipped to provide a flat floor suitable for vehicles and other rolling stock. Cargo is loaded through a large aft ramp that accommodates rolling stock, such as a 69-ton (63-metric ton) M1 Abramsmain battle tank, other armored vehicles, trucks, and trailers, along with palletized cargo.

C-17 Globemaster III cockpit

Maximum payload of the C-17 is 170,900 lb (77,500 kg), and its Maximum takeoff weight is 585,000 lb (265,350 kg). With a payload of 160,000 lb (72,600 kg) and an initial cruise altitude of 28,000 ft (8,500 m), the C-17 has an unrefueled range of about 2,400 nautical miles (4,400 km) on the first 71 aircraft, and 2,800 nautical miles (5,200 km) on all subsequent extended-range models that include a sealed center wing bay as a fuel tank. Boeing informally calls these aircraft the C-17 ER.[55] The C-17's cruise speed is about 450 knots (833 km/h) (Mach 0.74). It is designed to airdrop 102 paratroopers and their equipment.[56] The U.S. Army's Ground Combat Vehicle is to be transported by the C-17.

The C-17 is designed to operate from runways as short as 3,500 ft (1,064 m) and as narrow as 90 ft (27 m). In addition, the C-17 can operate from unpaved, unimproved runways (although with greater chance of damage to the aircraft).[56] The thrust reversers can be used to back the aircraft and reverse direction on narrow taxiways using a three- (or more) point turn. The plane is designed for 20 man-hours of maintenance per flight hour, and a 74% mission availability rate.[56]

The first production C-17 was delivered to Charleston Air Force Base, South Carolina on 14 July 1993. The first C-17 squadron, the 17th Airlift Squadron, became operationally ready on 17 January 1995.[57] The C-17 has broken 22 records for oversized payloads.[58] The C-17 was awarded U.S. aviation's most prestigious award, the Collier Trophy in 1994.[59] A Congressional report on operations in Kosovo and Operation Allied Force noted "One of the great success stories...was the performance of the Air Force's C-17A"[60] The C-17 flew half of the strategic airlift missions in the operation, the type could use small airfields, easing operations; rapid turnaround times also led to efficient utilization.[61]

C-17s delivered military goods and humanitarian aid during Operation Enduring Freedom in Afghanistan and Operation Iraqi Freedom in Iraq. On 26 March 2003, 15 USAF C-17s participated in the biggest combat airdrop since the United States invasion of Panama in December 1989: the night-time airdrop of 1,000 paratroopers from the 173rd Airborne Brigade occurred over Bashur, Iraq. The airdrop of paratroopers were followed by C-17s ferrying M1 Abrams, M2 Bradleys, M113s and artillery.[64] USAF C-17s have also been used to assist allies in their airlift requirements, including Canadian vehicles to Afghanistan in 2003 and Australian forces during the Australian-led military deployment to East Timor in 2006. In 2006, USAF C-17s flew 15 Canadian Leopard C2 tanks from Kyrgyzstan into Kandahar in support of NATO's Afghanistan mission. In 2013, five USAF C-17s supported French operations in Mali, operating with other nation's C-17s (RAF, NATO and RCAF deployed a single C-17 each).

A C-17 accompanies the President of the United States on his visits to both domestic and foreign arrangements, consultations, and meetings. The C-17 is used to transport the Presidential Limousine and security detachments.[65] There have been several occasions when a C-17 has been used to transport the President himself, temporarily gaining the Air Force One call sign while doing so.[66]

There was debate over follow-on C-17 orders, Air Force having requested line shutdown while Congress attempted to reinstate production. In FY2007, the Air Force requested $1.6 billion in response to "excessive combat use" on the C-17 fleet.[67] In 2008, USAF General Arthur Lichte, Commander of Air Mobility Command, indicated before a House of Representatives subcommittee on air and land forces a need to extend production to another 15 aircraft to increase the total to 205. Pending the delivery of the results of two studies in 2009, Lichte observed that the production line may remain open for further C-17s to satisfy airlift requirements.[68] The USAF eventually decided to cap its C-17 fleet at 223 aircraft, the final delivery was accepted on 12 September 2013.[69]

Boeing has marketed the C-17 to many European nations including Belgium, Germany, France, Italy, Spain and the United Kingdom. The Royal Air Force (RAF) has established an aim of having interoperability and some weapons and capabilities commonality with the USAF. The 1998 Strategic Defence Review identified a requirement for a strategic airlifter. The Short-Term Strategic Airlift (STSA) competition commenced in September of that year, however tendering was canceled in August 1999 with some bids identified by ministers as too expensive, including the Boeing/BAe C-17 bid, and others unsuitable.[70] The project continued, with the C-17 seen as the favorite.[70] In the light of Airbus A400M delays, the UK Secretary of State for Defence, Geoff Hoon, announced in May 2000 that the RAF would lease four C-17s at an annual cost of £100 million[67] from Boeing for an initial seven years with an optional two-year extension. The RAF had the option to buy or return the aircraft to Boeing. The UK committed to upgrading its C-17s in line with the USAF so that if they were returned, the USAF could adopt them.

RAF C-17 at RAF Lakenheath, August 2010

The first C-17 was delivered to the RAF at Boeing's Long Beach facility on 17 May 2001 and flown to RAF Brize Norton by a crew from No. 99 Squadron. The RAF's fourth C-17 was delivered on 24 August 2001. The RAF aircraft were some of the first to take advantage of the new center wing fuel tank found in Block 13 aircraft. In RAF service, the C-17 has not been given an official service name and designation (for example, C-130J referred to as Hercules C4 or C5), but is referred to simply as the C-17 or "C-17A Globemaster".

The RAF declared itself delighted with the C-17. Although the Globemaster fleet was to be a fallback for the A400M, the Ministry of Defence (MoD) announced on 21 July 2004 that they had elected to buy their four C-17s at the end of the lease,[71] even though the A400M appeared to be closer to production. The C-17 gives the RAF strategic capabilities that it would not wish to lose, for example a maximum payload of 169,500 lb (77,000 kg) compared to the A400M's 82,000 lb (37,000 kg).[67] The C-17's capabilities allow the RAF to use it as an airborne hospital for medical evacuation missions.[72]

Another C-17 was ordered in August 2006, and delivered on 22 February 2008. The four leased C-17s were to be purchased later in 2008.[73] Because of fears that the A400M may suffer further delays, the MoD announced in 2006 that it planned to acquire three more C-17s, for a total of eight, with delivery in 2009–2010. On 26 July 2007, Defence Secretary Des Browne announced that the MoD intended to order a sixth C-17 to boost operations in Iraq and Afghanistan.[74] On 3 December 2007, the MoD announced a contract for a sixth C-17,[75] which was received on 11 June 2008.[76]

On 18 December 2009, Boeing confirmed that the RAF had ordered a seventh C-17,[77][78] which was delivered on 16 November 2010.[79] The UK announced the purchase of its eighth C-17 in February 2012.[80] The RAF showed interest in buying a ninth C-17 in November 2013.[81]

The Royal Australian Air Force (RAAF) began investigating an acquisition of heavy lift aircraft for strategic transport in 2005.[84] In late 2005 the then Minister for DefenceRobert Hill stated that such aircraft were being considered due to the limited availability of strategic airlift aircraft from partner nations and air freight companies. The C-17 was considered to be favored over the A400M as it was a "proven aircraft" and in production. One major RAAF requirement was the ability to airlift the Army's M1 Abrams tanks; another requirement was immediate delivery. Though unstated, commonality with the USAF and the United Kingdom's RAF was also considered advantageous. RAAF aircraft were ordered directly from the USAF production run and are identical to American C-17 even in paint scheme, the only difference being the national markings. This allowed delivery to commence within nine months of commitment to the program.[85]

On 2 March 2006, the Australian government announced the purchase of three aircraft and one option with an entry into service date of 2006.[67] In July 2006 a fixed price contract was awarded to Boeing to deliver four C-17s for US$780M (A$1bn).[86] Australia also signed a US$80.7M contract to join the global 'virtual fleet' C-17 sustainment program[87] and the RAAF's C-17s will receive the same upgrades as the USAF's fleet.[88]

The Royal Australian Air Force took delivery of its first C-17 in a ceremony at Boeing's plant at Long Beach, California on 28 November 2006.[89] Several days later the aircraft flew from Hickam Air Force Base, Hawaii to Defence Establishment Fairbairn, Canberra, arriving on 4 December 2006. The aircraft was formally accepted in a ceremony at Fairbairn shortly after arrival.[90] The second aircraft was delivered to the RAAF on 11 May 2007 and the third was delivered on 18 December 2007. The fourth Australian C-17 was delivered on 19 January 2008.[91] All the Australian C-17s are operated by No. 36 Squadron and are based at RAAF Base Amberley in Queensland.[92]

On 18 April 2011, Boeing announced that Australia had signed an agreement with the U.S. government to acquire a fifth C-17 due to an increased demand for humanitarian and disaster relief missions.[93] The aircraft was delivered to the RAAF on 14 September 2011.[94] On 23 September 2011, Australian Minister for Defence Materiel Jason Clare announced that the government was seeking information from the U.S. about the price and delivery schedule for a sixth Globemaster.[95] In November 2011, Australia requested a sixth C-17 through the U.S. FMS program; it was ordered in June 2012, and was delivered on 1 November 2012.[96][97]

In August 2014, Defence Minister David Johnston announced the intention to purchase one or two additional C-17s.[100] On 3 October 2014, Johnston announced the government's approval to buy two C-17s at a total cost of US$770 million.[50] The United States Congress approved the sale under the Foreign Military Sales program.[101][102] Prime Minister Tony Abbott confirmed in April 2015 that two additional aircraft are to be ordered, with delivery in late 2015;[103] these are to add to the six C-17s it has as of 2015[update].[50]

Canada's air arm has had a long-standing need for strategic airlift for humanitarian and military operations around the world. It had followed a pattern similar to the German Air Force in leasing Antonovs and Ilyushins for many of its needs, including deploying the Disaster Assistance Response Team (DART) to tsunami-stricken Sri Lanka in 2005. The air service was forced to rely entirely on leased An-124 Ruslan for a Canadian Armydeployment to Haiti in 2003.[citation needed] The service has also used a combination of leased Ruslans, Ilyushins and USAF C-17s for moving heavy equipment into Afghanistan. In 2002, the Canadian Forces Future Strategic Airlifter Project began to study alternatives, including long-term leasing arrangements.[104]

RCAF CC-177 on approach to CFB Trenton

On 5 July 2006, the Canadian government issued a notice that it intended to negotiate directly with Boeing to procure four airlifters for the Canadian Forces Air Command (renamed Royal Canadian Air Force in August 2011).[105] On 1 February 2007, Canada awarded a contract for four C-17s with delivery beginning in August 2007.[106] Like Australia, Canada was granted airframes originally slated for the U.S. Air Force, to accelerate delivery.[107]

On 16 June 2007, the first Canadian C-17 rolled off the assembly line at Long Beach, California and into the paint hangar for painting and addition of Canadian markings including the national logo and air force roundel. The first Canadian C-17 made its initial flight on 23 July.[108] It was turned over to Canada on 8 August,[109] and participated at the Abbotsford International Airshow on 11 August prior to arriving at its new home base at 8 Wing, CFB Trenton, Ontario on 12 August.[110] Its first operational mission was delivery of disaster relief to Jamaica in the aftermath of Hurricane Dean.[111] The second C-17 arrived at 8 Wing, CFB Trenton on 18 October 2007. The last of four aircraft was delivered in April 2008.[112] The official Canadian designation is CC-177 Globemaster III.[113] The aircraft are assigned to 429 Transport Squadron based at CFB Trenton.

On 14 April 2010, a Canadian C-17 landed for the first time at CFS Alert, the world's most northerly airport.[114] Canadian Globemasters have been deployed in support of numerous humanitarian and military missions worldwide, including Operation Hestia after the earthquake in Haiti, providing airlift as part of Operation Mobile and support to the Canadian mission in Afghanistan. After Typhoon Haiyan hit the Philippines in 2013, Canadian C-17s established an air bridge between the two nations, deploying Canada's DART Team and delivering humanitarian supplies and equipment. In 2014, they supported Operation Reassurance and Operation Impact.[citation needed]

On 19 December 2014, it was reported that Canada's Defence Department intended to purchase one more C-17.[115][116] On 30 March 2015, Canada's fifth C-17 arrived at CFB Trenton.[117]

At the 2006 Farnborough Airshow, a number of NATO member nations signed a letter of intent to jointly purchase and operate several C-17s within the NATO Strategic Airlift Capability.[118] Strategic Airlift Capability members are Bulgaria, Estonia, Hungary, Lithuania, the Netherlands, Norway, Poland, Romania, Slovenia, the United States, as well as two Partnership for Peace countries Finland and Sweden as of 2010.[118] The purchase was for two C-17s, and a third was contributed by the U.S. On 14 July 2009, Boeing delivered the first C-17 under NATO's Strategic Airlift Capability (SAC) program. The second and third C-17s were delivered in September and October 2009.[119][120]

The SAC C-17s are based at Pápa Air Base, Hungary. The Heavy Airlift Wing is hosted by Hungary, which acts as the flag nation.[121] The aircraft are manned in similar fashion as the NATO E-3 AWACS aircraft.[122] The C-17 flight crew are multi-national, but each mission is assigned to an individual member nation based on the SAC's annual flight hour share agreement. The NATO Airlift Management Programme Office (NAMPO) provides management and support for the Heavy Airlift Wing. NAMPO is a part of the NATO Support Agency (NSPA).[123] In September 2014, Boeing revealed that the three C-17s supporting NATO SAC missions had achieved a readiness rate of nearly 94 percent over the last five years and supported over 1,000 missions.[124]

In June 2009, the Indian Air Force (IAF) selected the C-17 for its Very Heavy Lift Transport Aircraft requirement, it is to replace several types of transport aircraft.[125][126] In January 2010, India requested 10 C-17s through the U.S.'s Foreign Military Sales program,[127] the sale was approved by Congress in June 2010.[128] On 23 June 2010, the Indian Air Force successfully test-landed a USAF C-17 at the Gaggal Airport, India to complete the IAF's C-17 trials.[129] In February 2011, the IAF and Boeing agreed terms for the order of 10 C-17s[130] with an option for six more; the US$4.1 billion order was approved by the Indian Cabinet Committee on Security on 6 June 2011.[131][132] Deliveries began in June 2013 and are to continue until 2014.[133][134] In 2012, the IAF reportedly finalized plans to buy six more C-17s in the 13th five-year plan (2017–2022).[126][135][136]

The IAF's first C-17, 2013

The aircraft provides strategic airlift and the ability to deploy special forces, such as during national emergencies.[137] They are operated in diverse terrain – from Himalayan air bases in North India at 13,000 ft (4,000 m) to Indian Ocean bases in South India.[138] The C-17s are based at Hindon Air Force Station and are operated by the No. 81 Squadron Skylords.[139][140] The first C-17 was delivered in January 2013 for testing and training;[141] it was officially accepted on 11 June 2013.[142] The second C-17 was delivered on 23 July 2013 and put into service immediately. IAF Chief of Air Staff Norman AK Browne called the Globemaster III "a major component in the IAF's modernization drive" while taking delivery of the aircraft at Boeing's Long Beach factory.[143] On 2 September 2013, the Skylords squadron with three C-17s officially entered IAF service.[144]

The Skylords regularly fly missions within India, such as to high-altitude bases at Leh and Thoise. The IAF first used the C-17 to transport an infantry battalion's equipment to Port Blair on Andaman Islands on 1 July 2013.[145][146] Foreign deployments to date include Tajikistan in August 2013, and Rwanda to support Indian peacekeepers.[135] One C-17 was used for transporting relief materials during Cyclone Phailin.[147] The fifth aircraft was received in November 2013.[148] The sixth aircraft was received in July 2014.[149]

The C-17 played a crucial role in Operation Raahat, in which over 4,500 Indian nationals and 960 foreign nationals from 41 countries including US, UK, France, Canada and Egypt were evacuated from war-torn Yemen in April 2015.[150] C-17 also played a major role in supplying and rescuing during devastating 2015 Nepal earthquake, which killed nearly 6,000. C-17s were used to transport relief material and rescue Indian citizens.[151]

Boeing delivered Qatar's first C-17 on 11 August 2009 and the second on 10 September 2009 for the Qatar Emiri Air Force.[152] Qatar received its third C-17 in 2012, and fourth C-17 was received on 10 December 2012.[153] In June 2013, the New York Times reported that Qatar was allegedly using its C-17s to ship weapons from Libya to the Syrian opposition during the civil war via Turkey.[154] On 15 June 2015, it was announced at the Paris Airshow that Qatar agreed to order four additional C-17s from the five remaining "white tail" C-17s to double Qatar's C-17 fleet.[155][156]

In February 2009, the United Arab Emirates Air Force agreed to purchase four C-17s.[157] In January 2010, a contract was signed for six C-17s.[158] In May 2011, the first C-17 was handed over and the last of the six was received in June 2012.[159][160]

Kuwait requested the purchase of one C-17 in September 2010 and a second in April 2013 through the U.S.'s Foreign Military Sales (FMS) program.[161] The nation ordered two C-17s; the first was delivered on 13 February 2014.[162]

C-17A "ER": Unofficial name for C-17As with extended range due to the addition of the center wing tank.[55][164] This upgrade was incorporated in production beginning in 2001 with Block 13 aircraft.[164]

C-17B: Proposed tactical airlifter version. The design includes double-slotted flaps, an additional main landing gear on center fuselage, more powerful engines and other systems for shorter landing and take-off distances.[165] Boeing offered the C-17B to the U.S. military in 2007 for carrying the Army's Future Combat Systems (FCS) vehicles and other equipment.[166]

MD-17: Proposed variant for civilian operators.[167] Later re-designated as BC-17 after 1997 merger.[168]

On 10 September 1998, a U.S. Air Force C-17 (AF Serial No.96-0006) delivered Keiko the whale to Vestmannaeyjar, Iceland, a 3,800-foot (1,200 m) runway, and suffered a landing gear failure during landing. There were no injuries, but the aircraft received major damage to the landing gear. After receiving temporary repairs, the C-17 was flown to another city in Iceland for further repairs.[179][180]

On 10 December 2003, a U.S. Air Force C-17 (AF Serial No. 98-0057) was hit by a surface-to-air missile after take-off from Baghdad, Iraq. One engine was disabled and the aircraft returned for a safe landing.[181] The aircraft was repaired and returned to service.[182]

On 6 August 2005, a U.S. Air Force C-17 (AF Serial No. 01-0196) ran off the runway at Bagram Air Base in Afghanistan while attempting to land, destroying the aircraft's nose and main landing gear.[183] It took two months to make the aircraft flightworthy, the aircraft was flown to Boeing's Long Beach facility by a test pilot, as the temporary repairs imposed performance limitations.[184] In October 2006, the aircraft returned to service after receiving repairs.

On 30 January 2009, a U.S. Air Force C-17 (AF Serial No. 96-0002 – "Spirit of the Air Force") made a gear-up landing at Bagram Air Base.[185][186] The C-17 was ferried from Bagram AB, making several stops along the way, to Boeing's Long Beach plant for extensive repairs. The USAF Aircraft Accident Investigation Board concluded the cause was the crew's failure to lower the landing gear, having not followed the pre-landing checklist.[187]